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NGC 5931 (13,096 of 18,816)

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NGC 5931

NGC 5931, LEDA 55233, MCG+01-39-023

RA: 15h 29m 29.6s
Dec: +07° 34′ 23″

Con: Serpens
Ch: MSA:740, U2:199, SA:14

Ref: SIMBAD

(reference key)

Type: galaxy

Mag: B=15, V=?

Size: ?
PA: ?

History and Accurate Positions for the NGC/IC Objects (Corwin 2004)

NGC 5931 is not IC 1122 as is sometimes assumed from the NGC and IC data and descriptions. N5931 was found by Swift whose position for it is quite good. This is the brightest galaxy in the area, one of the so-called "cD" galaxies in a cluster. These objects average one to two magnitudes brighter than the second brightest galaxy in the clusters, so they are often quite outstanding from their several faint companions. This is certainly the case here since N5931 is at least a magnitude brighter than I1122, the second brightest in the cluster.

Next, Barnard, who was following an asteroid, ran across the brighter galaxy a few years after Swift. Barnard made a micrometric measurement of it and published it as a new object. His paper gives the position of his reference star as well as the offsets to the galaxy. The star's position is good, but the Dec offset is in error by 47 arcsec. This must reflect some sort of reduction error in Barnard's calculations as it appears to be a random number, not a clean digit error as we often see in the NGC and ICs. Fortunately, Barnard's description of the object mentions an 11th magnitude star 1 arcmin preceding. If we take the distance and magnitude of this star to be estimates (the actual separation is 2 arcmin and the magnitude is 13), then the object which Barnard saw is Swift's galaxy.

Finally, Bigourdan found a "nova" while measuring NGC 5931 (which he had no trouble identifying; his position is within an arcsecond of the GSC position). While Bigourdan's position for the new object is off by about 15 arcsec, he comments that because the nebula is so faint, it was difficult to measure. Even so, it is clearly a different object than NGC 5931, and so is not the same "new" object that Barnard saw.

Dreyer, however, faced with a micrometric measurement from Barnard, and an estimated position from Bigourdan (whose comparison star was not measured until GSC), agreeing to within about two arcmin, did the logical thing and adopted the micrometric measurement. So, the first IC includes the wrong position for IC 1122, credits its discovery to Barnard as well as to Bigourdan, and also includes Barnard's comment about the preceding star in the description.

In actuality, IC 1122 is a separate galaxy found by Bigourdan and given a pretty good position and description by him. I've adopted his object here.

Published comments

Photo index

Photo Index by Jim Lucyk: The Astrograph 12-1/1978/9 p35.

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 15.0 mag galaxy. Their coded description reads E,SLEL,BM.

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